Antimicrobial Resistance Profiles of Enterobacteriaceae in Surface Water From Streams and the Southern Gulf of Lake Tana, Ethiopia

Antimicrobial resistance (AMR) is a major global health concern, with resistant bacteria and genes spreading between humans, animals, and the environment. However, waterborne AMR in <i>Enterobacteriaceae</i> remains underexplored in developing countries such as Ethiopia. This study assessed the AMR profiles of <i>Enterobacteriaceae</i> isolated from 66 surface water samples collected from waste-receiving streams and the Gulf of Lake Tana. Bacteria were identified using standard microbiological methods, and antimicrobial susceptibility was tested by the Kirby-Bauer disk diffusion method. The most frequent isolates were Providencia alcalifaciens, Citrobacter spp., and Enterobacter spp. Resistance to first-generation cephalosporins ranged from 10.9% to 45.8% in stream isolates compared with 1.7% to 25.6% in lake isolates, while ceftriaxone resistance was detected in 13.5% and 4.5% of isolates, respectively. Among species, 30% of Escherichia coli, 22% of Enterobacter cloacae, and 12% of P. alcalifaciens were resistant to ceftriaxone, whereas resistance to cefazolin reached 40%, 67%, and 44%, respectively. Stream isolates also showed higher resistance to ampicillin (63%) and amoxicillin-clavulanic acid (29%) compared with lake isolates (50% and 12%). Overall, 44.8% of <i>Enterobacteriaceae</i> were multidrug-resistant. Significant differences in resistance were observed between stream and lake isolates for ciprofloxacin, ceftriaxone, trimethoprim-sulfamethoxazole, piperacillin-tazobactam, and cefazolin. The high prevalence of resistance to commonly used antibiotics, including third-generation cephalosporins, highlights the environmental dimension of AMR and underscores the urgent need for antimicrobial stewardship and surveillance in Ethiopia and similar settings.